This fell out of my front caliper when i was cleaning it.https://photos.google.com/photo/AF1QipP ... ky6h9j40vWI just put in on the caliper to photo it for scale.I had only removed the pads, not the lines or pistons.I've never seen anything like it on any of my other bikes. Is it supposed to do something? or just a free gift from the previous owner?

Hmmm, no idea where that's from, unless the calipers have been separated at some point and it was omitted during re-assembly, but if that were the case you'd be suffering fluid leakage and brake sponginess. It's about the right size for a caliper union, and that's the only thing that I can think of in that area that would use such an O-ring. Has anyone else any ideas?

Scotty wrote:Hmmm, no idea where that's from, unless the calipers have been separated at some point and it was omitted during re-assembly, but if that were the case you'd be suffering fluid leakage and brake sponginess. It's about the right size for a caliper union, and that's the only thing that I can think of in that area that would use such an O-ring. Has anyone else any ideas?

Thanks, It's very round in profile, I would have expected a caliper union to be pretty square.Nothing wrong with the brakes, so I'm not too worried, although posts about £40K compensation (which prompted me to clean my brakes) are a bit worrying!